The invention relates to the field of transistor circuits, and in particular to transistor circuits using organic semiconductors.
Transistor circuits using organic semiconductors (organic thin film transistors, OTFTs) have received intense interest for applications requiring structural flexibility, large area coverage, low temperature processing and especially low-cost. However, the operating voltage (20˜100 V) is usually too high, especially for portable, battery-powered device applications. Instead of using parylene, which has dielectric constant of 3, the use of high dielectric constant insulators as gate dielectrics would result in much reduced operating voltages for organic transistors. The basic requirements for such dielectric materials include the formation of thin, pinhole-free films with high breakdown voltage, low leakage current density and good long-term stability.
While there have been some early promising results with the deposition and integration, at or near room temperature, of metal oxides such as (Ba,Sr)TiO3 (BST) and HfO2 with organic semiconductors such as pentacene, either their dielectric constants were not as high as desired and/or the films were electrically leaky.